1. Field of the Invention
This invention relates to a water repellent agent for use in treating inorganic materials such as glass, ceramics and metals for imparting long-lasting water repellency and stain-proofness to their surface.
2. Prior Art
Various research endeavors have been made for enhancing the performance and expanding the applicable range of inorganic materials such as glass, ceramics and metals by treating the inorganic materials at their surface with various surface treating agents for improving surface properties. One typical technique is to treat an inherently hydrophilic surface with a silicone composition for modifying the surface to be water repellent.
Japanese Patent Application Kokai (JP-A) Nos. 147484/1983, 221470/1985 and 96935/1992 disclose that polysiloxanes and polysilazanes having a perfluoroalkyl group excel in water repellency. These water repellent agents are excellent in water repellency, but less effective in allowing water droplets to fall down. When they are applied to glazing in houses and buildings as stain-proof treating agents, water droplets tend to stay on the glazing surface as dots instead of falling down. Then the glazing is undesirably stained because dust, debris and oil in the atmosphere can adhere to such water droplets.
Also fluorinated silazane compounds are disclosed in JP-A 290437/1991. Although these compounds eliminate the above-mentioned drawback, they are substantially insoluble in conventional organic solvents. They are soluble only in Freons currently under federal restriction such as 1,1,3-trichlorotrifluoroethane and expensive fluorinated hydrocarbons. This limits the application range.
Japanese Patent Publication (JP-B) No. 15473/1975 discloses a mixture of dimethylpolysiloxane and strong acid. This mixture is superior in water repellency and water droplet falling, but is less durable in a sense that its action does not last long.
JP-B 38950/1977 discloses a stain-proof processing composition comprising a perfluoroalkoxysilane, an alkoxysilane, and a diol. JP-A 233535/1990 discloses a glass surface treating composition comprising a silane having a perfluoroalkyl group, an organopolysiloxane, an acid, and a volatile organic solvent. JP-A 144940/1992 discloses a water- and oil-repellent composition comprising an organopolysiloxane, a silane or siloxane containing a perfluoroalkyl group, and an acid. These compositions have superior water repellency, but fail to maintain that repellency for a long term.
There is a need to develop an agent which is durably water repellent.
Therefore, an object of the present invention is to provide a water repellent agent which is effective for treating inorganic materials to render their surface water repellent, allow water droplets on their surface to fall down, and impart durable water repellency and stain-proofness to their surface and which is soluble in ordinary organic solvents.